The invention relates to an apparatus and method for forming of a vehicle's driveshaft having an elongated shaft and two coupling end parts. This is achieved, in accordance with the invention, by a pulsed magnetic force (PMF) process.
A vehicle's driveshaft, having the general structure as outlined above, is commonly manufactured by welding ends of a cylindrical shaft to coupling end parts. Conventional welding is a time consuming and relatively expensive process.
Furthermore, the workpieces are typically heated in this process and therefore at times cooling installations need to be included.
A known way of rapid “cold” joining or welding of workpieces to one another is by the use of a PMF process. By this technology, a very short and intense electric pulse is discharged through a coil and this discharge induces eddy currents in a workpiece which yield magnetic repulsion between the electric coil and the workpiece. This repulsion then deforms the workpiece proximal to the forming coil causing its surface to rapidly move and impinge on another workpiece whereby it either pressure joins, and with higher energy surface welds to the other workpiece.
A particular application of this process is in joining or surface welding of a tubular workpiece onto a cylindrical one contained therein by inducing inward radial deformation of the tubular workpiece. PMF processes and some specific applications thereof are disclosed in the following U.S. Pat. No.: 3,654,787 (Brower), U.S. Pat. No. 3,961,639 (Leftheris), U.S. Pat. No. 4,170,887 (Baranov), U.S. Pat. No. 4,531,393 (Weir), U.S. Pat. No. 4,807,351 (Berg et al.), U.S. Pat. No. 5,353,617 (Cherian et al.), U.S. Pat. No. 5,442,846 (Snaper) and U.S. Pat. No. 5,824,998 (Livshitz et al.).
A specific application of the PMF process for the purpose of joining components for a vehicle's driveshaft is described in U.S. Pat. No. 5,981,921.
There are some specific problems in the realization of the PMF process for forming a driveshaft in that the end pieces radially protrude beyond the circumference of the shaft. In order to utilize the PMF process, the forming coil should be brought into close proximity to the deformed workpiece and in this case this means that the forming coil needs to be closely fitted around the shaft. After joining or surface welding of the shaft and the coupling end part, it is not possible, with the prior art methods, to release the coil turnover and the driveshaft. This is the reason, that the PMF process has not yet found a true application in practice in the field of forming of driveshafts.